Description of the Art
Fluid ejection cartridges typically include a fluid reservoir that is fluidically coupled to a substrate. The substrate normally contains an energy-generating element that generates the force necessary for ejecting the fluid through one or more nozzles. Two widely used energy-generating elements are thermal resistors and piezoelectric elements. The former rapidly heats a component in the fluid above its boiling point creating a bubble causing ejection of a drop of the fluid. The latter utilizes a voltage pulse to move a membrane that displaces the fluid resulting in ejection of a drop of the fluid.
Currently there is a wide variety of highly efficient inkjet printing systems in use. These systems are capable of dispensing ink in a rapid and accurate manner. However there is also a demand by consumers for ever-increasing improvements in reliability and image quality, while providing systems at lower cost to the consumer. In an effort to reduce the cost and size of ink jet printers, and to reduce the cost per printed page, printers have been developed having small moving printheads that are typically connected to larger stationary ink supplies. This development is called xe2x80x9coff-axisxe2x80x9d printing, and has allowed the larger ink supplies, xe2x80x9cink cartridges,xe2x80x9d to be replaced as it is consumed without requiring the frequent replacement of the costly printhead, containing the fluid ejectors and nozzle system.
Improvements in image quality have typically led to an increase in the organic content of inkjet inks. This increase in organic content typically leads to inks exhibiting a more corrosive nature, potentially resulting in the degradation of the materials coming into contact with such inks. Degradation of these materials by more corrosive inks raises reliability and material compatibility issues. These material compatibility issues generally relate to all the materials the ink comes in contact with. However, they are exacerbated in the printhead because, in an off-axis system, the materials around the fluid ejectors and nozzles need to maintain their functionality over a longer period of time. This increased reliability is necessary to ensure continued proper functioning of the printhead, at least through several replacements of the ink cartridges. Thus, degradation of these materials can lead to potentially catastrophic failures of the printhead.
Improvements in image quality have also typically resulted in demand for printheads with fluid ejector heads capable of ejecting smaller fluid drops. Generally, this is accomplished by decreasing the size of the resistor as well as decreasing the size and thickness of the fluid chamber surrounding the resistor. In addition, the size and thickness of the orifice or bore, through which the fluid is ejected, is also typically reduced to eject smaller drops. A fluid ejector head is typically fabricated utilizing conventional semiconductor processing equipment. Typically, etching or removing a conductor material creating an area of higher resistance forms the thermal resistor. A dielectric passivation layer is then typically deposited over the conductors and the resistor to provide electrical isolation and environmental protection from degradation by the fluid located in the fluid chamber. As the resistors and chambers become smaller the ability to maintain thickness uniformity in the various layers, because of step coverage issues, becomes more difficult. All of these problems can impact the manufacture of lower cost, smaller, and more reliable printer cartridges and printing systems.